[FFmpeg-devel] [PATCH v2 2/5] avdevice/alsa_dec: make sure we have enough data in non-blocking mode

[Marton Balint]

On Mon, 1 Mar 2021, Marton Balint wrote:

> Otherwise we might return 1-2 samples per packet if av_read_frame() call rate is
> only sligthly less than the stream sample rate.

Ping for this and the rest of the series. Note that the approach in 
this patch makes 1/5 unneeded because constant frame size is now indeed 
guaranteed.

Regards,
Marton

>
> Signed-off-by: Marton Balint <cus at passwd.hu>
> ---
> libavdevice/alsa.c     |  5 +++++
> libavdevice/alsa.h     |  1 +
> libavdevice/alsa_dec.c | 22 ++++++++++++----------
> 3 files changed, 18 insertions(+), 10 deletions(-)
>
> diff --git a/libavdevice/alsa.c b/libavdevice/alsa.c
> index 117b2ea144..ee282fac16 100644
> --- a/libavdevice/alsa.c
> +++ b/libavdevice/alsa.c
> @@ -286,6 +286,10 @@ av_cold int ff_alsa_open(AVFormatContext *ctx, snd_pcm_stream_t mode,
>         }
>     }
> 
> +    s->pkt = av_packet_alloc();
> +    if (!s->pkt)
> +        goto fail1;
> +
>     s->h = h;
>     return 0;
> 
> @@ -308,6 +312,7 @@ av_cold int ff_alsa_close(AVFormatContext *s1)
>     if (CONFIG_ALSA_INDEV)
>         ff_timefilter_destroy(s->timefilter);
>     snd_pcm_close(s->h);
> +    av_packet_free(&s->pkt);
>     return 0;
> }
> 
> diff --git a/libavdevice/alsa.h b/libavdevice/alsa.h
> index 1ed8c82199..07783c983a 100644
> --- a/libavdevice/alsa.h
> +++ b/libavdevice/alsa.h
> @@ -58,6 +58,7 @@ typedef struct AlsaData {
>     void *reorder_buf;
>     int reorder_buf_size; ///< in frames
>     int64_t timestamp; ///< current timestamp, without latency applied.
> +    AVPacket *pkt;
> } AlsaData;
> 
> /**
> diff --git a/libavdevice/alsa_dec.c b/libavdevice/alsa_dec.c
> index 6d568737b3..88bf32d25f 100644
> --- a/libavdevice/alsa_dec.c
> +++ b/libavdevice/alsa_dec.c
> @@ -104,34 +104,36 @@ static int audio_read_packet(AVFormatContext *s1, AVPacket *pkt)
>     int64_t dts;
>     snd_pcm_sframes_t delay = 0;
> 
> -    if (av_new_packet(pkt, s->period_size * s->frame_size) < 0) {
> -        return AVERROR(EIO);
> +    if (!s->pkt->data) {
> +        int ret = av_new_packet(s->pkt, s->period_size * s->frame_size);
> +        if (ret < 0)
> +            return ret;
> +        s->pkt->size = 0;
>     }
> 
> -    while ((res = snd_pcm_readi(s->h, pkt->data, s->period_size)) < 0) {
> +    do {
> +        while ((res = snd_pcm_readi(s->h, s->pkt->data + s->pkt->size, s->period_size - s->pkt->size / s->frame_size)) < 0) {
>         if (res == -EAGAIN) {
> -            av_packet_unref(pkt);
> -
>             return AVERROR(EAGAIN);
>         }
> +        s->pkt->size = 0;
>         if (ff_alsa_xrun_recover(s1, res) < 0) {
>             av_log(s1, AV_LOG_ERROR, "ALSA read error: %s\n",
>                    snd_strerror(res));
> -            av_packet_unref(pkt);
> -
>             return AVERROR(EIO);
>         }
>         ff_timefilter_reset(s->timefilter);
> -    }
> +        }
> +        s->pkt->size += res * s->frame_size;
> +    } while (s->pkt->size < s->period_size * s->frame_size);
> 
> +    av_packet_move_ref(pkt, s->pkt);
>     dts = av_gettime();
>     snd_pcm_delay(s->h, &delay);
>     dts -= av_rescale(delay + res, 1000000, s->sample_rate);
>     pkt->pts = ff_timefilter_update(s->timefilter, dts, s->last_period);
>     s->last_period = res;
> 
> -    pkt->size = res * s->frame_size;
> -
>     return 0;
> }
> 
> -- 
> 2.26.2
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".